Electric wave guide



Jan. 17, 1950 E. C. CORK ET AL ELECTRIC WAVE GUIDE Filed April 18, 1945 /f IN VEN TOR. Edu/arab Cor/f,

Bowman-Manifold A T TOR/VE K Patented Jan. 17, 1950 UNITED STATES PATENT OFFICE ELECTRIC WAVE GUIDE Application April 18, 1945, Serial No. 589,069 In Great Britain September 1, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires September 1, 1962 7 Claims. l

This invention relates to electric wave guides which are employed for transmitting electro-magnetic energy of very high frequency. The invention is exclusively concerned with the type of wave guide consisting of a hollow metallic conductor.

1t has been found necessary to provide for the rotation of a section of a wave guide with respect to an adjacent section. For example, in a transmitting or receiving system where the energy transmitted or received is picked up by a wave guide it may be desired to associate with said wave guide a reflector for the transmitted or received energy and to cause the wave guide and the reflector to be rotated during transmission or reception. With such a construction it is desirable that the transmitter and receiver be located at a point remote from the transmitting or receiving portions of the wave guide and their associated reflectors and consequently the provision of means which enable one section of the Wave guide to be rotated with respect to another section becomes necessary. It has been found impracticable for a variety of reasons to arrange the relatively rotatable sections of the wave guide in electrical contact with one another since in the first place such contacting sections Will give rise to impedance variations at their points of contact and, furthermore, due to their frictional engagement they will give rise to the introduction of undesirable electrical noise.

It is therefore the object of the present invention to provide for the relative rotation of two sections of a wave guide without having the two sections in electrical contact and without the introduction of undesirable impedance changes and without permitting the escape of a substantial amount of energy.

According to the invention an electric wave guide is provided having two adjacent sections mounted for relative rotational movement, said sections having overlapping surfaces which are not in contact with one another, said overlapping surfaces having such dimensions as to afford an effective short circuit at the adjacent ends of the sections of the ,wave guide. The overlapping surfaces are air-spaced and sin-ce the two sections of the wave guide are not in contact with one another undesirable electrical noise such as referred to above is not produced and as stated by suitablychoosing the dimensions of the overlapping surfaces an effective short-circuit is provided at adjacent ends of the sections so that no substantial impedance variation is produced at the adjacent ends of the sections and the escape of a substantial amount of energy is prevented.

In order that the said invention may be clearly understood and readily carried into effect various examples according to the invention will now be described with reference to the accompanying drawings in which:

Figure 1 shows a longitudinally sectional View through two sections of a wave guide lconstructed in accordance with the invention,

Figures 2, 3 and 4 are similar views illustrating modified forms of the invention and,

Figure 5 is a view of a transmitting and receiving apparatus embodying the construction shown in Figure 1.

Referring now to Figure 1 of the drawings, the reference numeral G indicates one section of a Wave guide which comprises a hollow tubular conductor of circular form in cross section and which may be used for the transmission of waves, in particular waves of the E01 mode. The reference numeral 'l indicates a similar section of wave guide, the adjacent ends of the two sections being spaced apart as shown and provided with annular flanges 8 and 9, as shown. The flanges 8 and 9 provide the overlapping surfaces referred to above. In general, a wave transmitted past the gap between the adjacent ends 6 and 'l tends to radiate a small portion of its energy through the gap, and further, the gap presents an impedance to the longitudinal surface currents set up in the guide. In the construction shown in Figure 1 in order to maintain the impedance at a minimum and in order to prevent a substantial escape of energy via the gap, the distance between the two flanges is small and is constant, throughout the area of the anges and the radial depth of the flanges is so chosen that it effectively provides a quarter wave-length line open-circuited at the end remote from the adjacent ends of the sections 6 and l. A quarter-wavelength line opencircuited at one end effectively provides a short circuit at the opposite end and, consequently, in the construction shown in Figure 1 an effective short circuit is presented at the ladjacent ends of the sections 6 and l. Where, for example, the wave guide has a suitable diameter for the transmission of energy of a free space wave length vof 3.2 centimeters, the distance apart of the flanges 3 and 9 may be half a millimetre and the flanges may be approximately 8 millimetres in radial depth. With the construction shown one section can thus be rotated relatively to the other section and since there is no direct contact between the two sections the introduction of electrical noise as referred to above is avoided, and moreover, a minimum impedance is introduced in the guide.

Figure 2 of the drawings illustrates a modied form of the invention in which the vflanges 8 and 9 are composed of an odd integral number of quarter wavelength portions and are shaped to present a so-called labyrinth construction. The length of the portions of the labyrinth should Abe chosen so that the portions X and Y are-approximately equal to a quarter-wavelength of the energy transmitted along the guide. Also in order that the arrangement should cause a minimum disturbance to the waves transmitted along the guide and in order to reduce the escape of energy to a minimum, the portions X should have a larger spacing than the portions Y so that a wave tending to escape suffers repeated reflections and -is thus substantially attenuated due to the unequal characteristic impedances of the portions X and Y.

Figure 3 shows a further modification of the invention in which the anges i3 and 9 are again composed of an odd integral number of quarter wavelength portions. In the example shown in Figure 3 the flanges are formed from three quarter wavelength portions and the distance between the two anges at the central portion is not constant since the flange 9 is provided with an annular protrusion I which makes the characteristic impedance of the central portion different from that of the other portions so as to cause repeated reflection of a wave tending to escape.

It is not necessary that the overlapping surfaces afforded by the flanges 8 and Si should lie, in general, in a plane transverse to the axis of the guide since the effect of the invention can be obtained if the overlapping surfaces are, in general, concentric with the axis of the guide.

Figure 4 of the drawings illustrates a construction of this latter form from which it will be observed that the section 6 is `provided with an extension II of large diameter which receives the adjacent end of the section i'. In this case the length of the section I l is chosen to be effectively equal to a quarter-wavelength of the energy transmitted along the guide.

Figure 5 of the drawings illustratesapparatus for vtransmitting and receiving high frequency energy with which the invention may be employed. In this apparatus a transmitting aerial I2 is vemployed which comprises a wave guide section having aslot I3 Vthrough which energy isiradiated. The aerial I2 is disposed at the focus of a parabolic reflector Ill which causes the energy to be radiated in a desired direction. The receiving aerial I5 also comprises a wave guide section provided with a slot I 6 whichis disposed at the focus of a further parabolic reflector Ii'. The energy transmitted from the aerial I2 is fed thereto through a wave guide section I3 and the energy picked up by the receiving aerial l 5 is fed therefrom to a wave guide section Iii, the sections I8 and i9 being connected respectively to a tra-nsmitting and receiving apparatus located at apoint remote from the aerials i2 Aand l5. It is desirable in operation of the apparatus shown in Figure 3 to rotate the reiiectors 'I and Ii' and their associated aerials relatively to the guide sections i8 `and I 9. For lthis purpose a suitable motor Zi is provided which is'so coupled to the reflectors I4 and Ii' and their associated aerials as to'cause the latter to rotate relatively to the wave guide sections I8 'and I9. To permit of the rotation of the wave guide sections .forming the aerials i2 and l5 with respect to the stationary wave guide 4save to support the rotatable sections and also serve to afford water-tight glands. It will thus be appreciated that by the provision of the invention it is `possible to effect rotation of the aerials I-2 and i5 whilst permitting the transmitting and .receiving apparatus to remain stationary and to be'located at a point remote from the aerials and without introducing the disadvantages referred to above.

What we claim is:

Vl. An yelectric wave guide devoid of any inner Yconductor and having two adjacent sections mounted for relative rotational movement, said sections having annular flanges on the adjacent ends thereof, at least one of said flanges having a raised annular surface portion connected to the body of the flange by substantially cylindrical surface portions, the radial width of said annular surface `portion being effectively equal lto a quarter-wavelength of the energy to be transmitted along the guide andthe spacing between said annular surface portion and the corresponding surface of the opposing flange being different than the spacing between the remaining portions of the flanges to provide different characteristic `impedances thereby to Iprovide repeated reflection of the energy passing bctween said flanges.

2. A wave guide in the form of a num-ber of hollow conductive .tubes arranged in a coaxial end-to-end relationship, said tubes being rotatable with respect to one another about their common axis, said tubes being provided with overlapping surfaces at their vadjacent ends, said surfaces lhaving a narrow gap therebetween, the eX- tent of overlap of said surfaces being equal to an odd integral number of straight quarter wavelength portions, said straight portions being arranged to vform a zig-zag passageway from the interior of said tubes to ambient space, to provide series connected sections of said gap having different characteristic irnpedances `so as to cause repeated reflection of energy which tends to escape through said gap.

3. A wave guide structure having two abutting coaXially arranged sections arranged'for relative movement about the aXis of said sections and complementary conductive flange members afliXed to the adjacent ends of said sections, said conductive ange members having a plurality of annular surface portions located alternately in two planes and a plurality of cylindrical surface portions parallel Ito the axis of said structure interconnecting the annular surfaces, the radial dimensions of said annular surface portions and the heights of said cylindrical surface portions being substantially a 'quarter wavelength at the operating frequency, said :cylindrical surface portions being spacedapart by la distance diiierent from that by whichlthe'annular surface portions are spaced.

'4. In a hollow-pipe wave guide, two abutting coaxial sections one of whichis rotated on a longitudinal axis while the other remains stationary, and a conductiveflange individual to each one of the abutting ends of said sections, said anges being provided with complementary annular rib and `channel surfacesthe axial and radial `dimension 'of saidrrib `and channelsurfaces being substantially equal toa quarter of the operating wavelength and the annular surfaces being spaced apart to a different degree than the cylindrical surfaces between said annular surfaces whereby an effective short circuit is formed between said sections.

5. A wave guide structure having two abutting sections coaxially arranged for relative rotational movement about the axis of said sections, and complementary conductive flange members arranged on adjacent ends of said abutting sections, said flange members having annular land and groove portions connected by cylindrical wall portions, the land portions of one flange nesting within the groove portions of the other, the widths of said land and groove and wall portions being substantially equal to a quarter Wavelength of the energy transmitted along the guide, the spacing between said land and said groove portions being different than that between adjacent wall portions.

6. A hollow pipe Wave guide comprising two sections having overlapping conductive flanges mounted on adjacent ends thereof, said two flanges being out of mutual contact and having telescoped annular groove and land portions connected by axially arranged cylindrical portions, said flanges being so dimensioned that each groove or land or cylindrical portion is approximately equal to a quarter-wavelength of the energy transmitted along the guide, the spacing between land and groove portions being greater than the spacing between cylindrical portions.

7. A hollow pipe wave guide having two sections having overlapping conductive anges mounted on adjacent ends thereof, said two anges being out of mutual contact and having in a plane passing radially through the axis of the guide a crosssection forming short straight gaps connected in series, the length of each of said gaps being approximately equal to a quarter-wavelength of the energy transmitted along the guide and the width of the gaps extending radially of said guide being greater than the width of the gaps extending axially thereof.

vEDWARD CECIL CORK.

MICHAEL BOWMAN-MANIFOLD.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,155,508 Schelkunoff Apr. 25, 1939 2,155,821 Goldsmith Apr. 25, 1939 2,281,274 Dallenbach et al. Apr. 28, 1942 2,351,895 Allerding June 20, 1944 2,401,344 Espley June 4, 1946 2,402,540 Espley June 25, 1946 2,407,318 Mieher Sept. 10, 1946 2,434,925 Haxby Jan. 27, 1948 

